Deoxyribonucleic acid, or DNA, is referred to as a blueprint because it contains the entire set of instructions that specify the inherent characteristics and traits that an organism will possess after birth. DNA is analogous to an architect's technical plans that contains all the details on how to construct a house. Like an architect's blueprint, DNA also contains all the information for building a complete functional organism.
DNA is a double-helix stranded molecule stored in the nucleus of the cells of all living things. In the human body, which contains around 5 trillion cells, DNA is condensed around protein complexes called histones, to form structures known as chromosomes. Each individual human being contains 46 chromosomes grouped into pairs. A pair of sex chromosomes, or the X and Y chromosomes, determine a person's biological gender, whether the individual is a male or a female. All the other 22 pairs are referred to as autosomes.
Chromosomes are composed of genes, which are the fundamental units of heredity. There are approximately 20,000 to 25,000 genes in the body. These microscopic structures are sections of DNA that code for a certain protein, which is subsequently expressed as a particular trait, such as hair, eye or skin color. Majority of an individual's genetic features are inherited from the parents.